FXUS65 KBOU 210620

AFDBOU



Area Forecast Discussion

National Weather Service Denver/Boulder CO

1220 AM MDT Sun Jun 21 2026



.KEY MESSAGES... 



- Critical fire weather conditions are expected for the mountains

  and high valleys today. 

 

- Strong to severe storms possible across the eastern plains

  today and Sunday. For today, very large hail, damaging wind 

  gusts, and a couple of tornados possible across the far 

  northeast plains. 

 

- Scattered coverage of showers and storms on Monday and most of 

  next week across the plains. 



- Elevated fire weather conditions possible for the mountains and

  high valleys most of next week. 



&&



.DISCUSSION /Through Saturday/...

Issued at 1259 PM MDT Sat Jun 20 2026



Visible satellite imagery shows mid level clouds over the 

northern and central mountains of Colorado indicating mid level 

instability. Some weak showers have develop mainly over the 

foothills with some briefly making it onto the plains before 

dissipating. While a couple of these showers could grow strong 

enough to create some lightning, they will stay below severe 

limits across all of the foothills and I-25 corridor. 



There are two other significant features to note in the

observations and satellite data. One is a DCVZ that has setup over

the far southeast side of the Denver metro. Winds remain from the

northwest to northeast to the north of this boundary with dew

points staying in the low 50s. To the south of this boundary,

southwest winds have developed with much warmer temperatures and

dew points in the 30s. This is the boundary that will create the

initial strong to severe storms today. Storms will begin in Elbert

and Arapahoe Counties and as they encounter much greater

instability in Lincoln and Washington Counties, they will grow

strong to severe. Large hail and strong winds will be the primary

threat from these storms although a tornado cannot be ruled out. 



The other feature worth noting is a warm front-like feature that

is an east-west oriented boundary over the border of 

Washington/Logan Counties and Phillips/Yuma Counties. Low clouds 

have persisted for the entire morning to the north of this 

boundary keeping temperatures in the low 70s to upper 60s and dew 

points in the low 60s. To the south of this boundary, temperatures

are in the upper 80s to low 90s with dew points in the 50s. The 

parameter space near and just north of this boundary is 

exceptional for Colorado standards. Mixed-layer CAPE is forecast 

to be around 2,500-3,000 j/kg. Deep layer shear will be above 50 

knots to the north of this boundary and may approach 60 knots. 

Plus, the boundary has greatly increased the low level helicity 

with effective helicity values forecast to be 300-400 m2/s2. Any 

storm that forms in this area will be capable of very large hail 

up to baseball size, damaging wind gusts up to 70 mph, and a 

supercell tornado. The Storm Prediction Center has highlighted 

this area in an enhanced risk of severe weather for good reason. A

convective watch will be needed later this afternoon for this 

area. The one factor that may limit the chance of severe weather 

in this area is a lack of a lifting mechanism during the 

afternoon. There is a somewhat significant cap on soundings and 

convective initiation this afternoon is uncertain. Storms may not 

form until later this evening when storms that initiate north of 

Cheyenne, WY reach that area. If storm initiation doesn't occur 

until this evening, the main risk would be very large hail. 



A shortwave trough will move through our forecast area tonight

and there will be slight subsident flow tomorrow morning. West

winds will mix down in the morning hours which will clear any fog

or low clouds that develop across the eastern plains tonight. A

dryline will setup roughly from Sterling to Limon which may

initiate storms. Mixed-layer CAPE values around 1,500 j/kg will

support the formation of a couple of strong to severe storms to

the east of the dryline. The main threats would be large hail and

damaging wind gusts. Otherwise, temperatures will be slightly

above normal in the Denver metro with a limited chance of rain. 



Low level winds will have an easterly component Monday through

Thursday of this upcoming week. This will keep healthy moisture in

place over the eastern plains of Colorado. The moisture and

upslope flow will generate daily afternoon/evening showers and

thunderstorms. This will also keep temperatures below normal most

days. There may be a severe threat from some of these storms but

any details about this threat is unknown at this time. 



&&



.AVIATION /06Z TAFS through 06Z Monday/...

Issued at 1208 AM MDT Sun Jun 21 2026



Low stratus clouds with bases 008-020 are present across much of

the Denver metro area with SCT-BKN coverage. The duration of these

is rather uncertain and hinges on the consistency and strength of

any drainage flow that develops. Winds currently are retaining a

NE and N component but speeds are weakening and a gradual

counter-clockwise rotation to SW drainage flow is expected between

08-11Z. Forecast is for low clouds to largely dissipate past 12Z,

with 14Z being the latest possible return to VFR conditions.



This afternoon, winds should be out of the NW to N and gusty with

some gusts up to 25 kts looking likely for most of the afternoon.

There is a very low chance of showers/thunderstorms tomorrow 

afternoon, but are currently expected to stay south and east of 

the terminals.



&&



.BOU WATCHES/WARNINGS/ADVISORIES...

None.



&&



$$



DISCUSSION...Danielson

AVIATION...BRQ